Field of the Invention
The present invention relates to a substrate using a surface-treated fiber film, and a semiconductor apparatus using the same.
Description of the Related Art
With remarkable progress of digital technology, miniaturization and higher performance of electronic devices represented by personal computers and mobile phones have been required. For example, for a printed wiring substrate which is a representative part of these electronic devices, there is a strong demand for improving characteristics of a glass fiber film which is a constitutional part of the printed wiring substrate in order to cope with the above-mentioned high density mounting and miniaturization. Also, speed up and high frequency of a computer, a mobile, communication infrastructures, etc., have advanced, and accompanied by this, it has been required to the printed wiring substrate to be a low dielectric material which decreases transmission loss. There is also a demand for a glass fiber film having low thermal expansion characteristics and high tensile rigidity characteristics. Further, it has earnestly been required to develop a thinner glass fiber film.
In addition, as represented by a semiconductor package for mobile phones in recent years, accompanied by high density mounting, miniaturization and higher performance of a semiconductor package, and a demand for a printed wiring substrate to be used is increasing. For example, to prevent warpage of a package after mounting from occurring, a substrate material having a lower linear expansion has been required, and to meet the requirement, a laminated substrate in which an organic resin composition into which an inorganic filler has been highly filled is impregnated into a glass fiber has been employed. However, since the resin composition has high viscosity, it generates unfastening or twisting of the glass fiber, and as a result, there are problems that uniformity of the substrate is impaired and the package is warped by inner shear stress.
With regard to the prior art relating to the present invention, there may be mentioned, for example, those described in the Patent Documents mentioned below. For the printed wiring substrate using glass fiber, in addition to high heat resistance, light resistance and impact resistance, heat conductivity, etc., have been also required accompanied by the use of high power modules in recent years. In fact, there are disclosed a white film and a metal laminate having a low linear expansion coefficient, which contain a thermoplastic resin or an epoxy resin, and a filler (Patent Documents 1 to 4). Also, there is disclosed a glass cloth having high whiteness by impregnating a metal salt into the glass cloth and drying, thereafter impregnating a silicone coupling agent into the same and drying, and a process for manufacturing a laminated substrate using the same (Patent Document 5). Further, there is disclosed a white substrate which comprises a UV absorber or a photostabilizer being contained in one surface of a white film comprising an acrylic copolymer and a filler (Patent Document 6). However, the epoxy resin or the thermoplastic resin has low heat discoloration resistance, etc., so that it cannot be used as a white substrate and a laminated substrate, and as a material for a high performance printed substrate having good heat resistance, only a ceramics substrate, etc., is present. However, the ceramic substrate involved the problems in processability, strength, discoloration resistance, etc.
As the conventional process for manufacturing the metal clad laminated substrate, there has widely been used a method in which an uncured state prepreg which is prepared by impregnating an epoxy resin, a phenol resin or a silicone resin, which are resins, into a glass fiber and drying the same, and a copper foil which is a metal layer are laminated, heated and pressed under pressure. In particular, a copper clad glass epoxy substrate in which an epoxy resin is impregnated into the glass fiber has generally been used. However, in recent years, a highly heat resistant substrate has been required in the points of employment of a lead-free solder having a high melting point, and heat generation of the device due to higher performance. The glass epoxy substrate has a glass transition temperature of around 200° C., and has a characteristic that it is easily discolored, so that there is a problem in heat resistance. Thus, a glass epoxy substrate in which an inorganic filler had been highly filled has been employed for the purpose of heat dissipation.
In the glass fiber to be used for the metal clad laminated substrate, a method of surface treating the fiber by a silane coupling agent has been employed to heighten affinity with the resin, and an attached amount thereof is generally 0.05 to 0.25% by mass (Patent Document 7). The conventional surface-treated glass fiber itself does not have self-standing property, and the fiber is not fixed. Therefore, when the resin into which an inorganic filler is highly filled is impregnated into the glass fiber, and after preparing an uncured state prepreg, the material is pressed under heating and pressure as mentioned above, unfastening and twisting are generated. Also, due to inner shear stress, twisting and warpage were generated to the substrate itself, and there was a problem that the characteristics become ununiform in the substrate.
Further, there is a problem that deformation or expansion occurs at high temperature, and dimensional stability of the substrate is lowered. To solve the problem of the dimensional stability, it has been proposed a method of using a glass cloth in which a count of twist of the glass fiber, and a ratio of the picks of the warp and the weft yarn are defined (Patent Document 8). When such a glass cloth is used, dimensional stability or solder heat resistance of the cloth itself at high temperature becomes good. However, it is necessary to have a specific fiber structure and weave structure, and fixation of the fiber has not yet been made, so that there remains a doubt in dimensional stability of the resin into which an inorganic filler is highly filled as mentioned above.
On the other hand, as a substrate for mounting which is required to have heat resistance, ceramics has also been used but it is expensive and is in a situation that it cannot correspond to a large-sized substrate in the aspect of processability.
Further, in recent years, there has been investigated a metal clad laminated substrate using a silicone resin, which is excellent in characteristics such as heat resistance, weather resistance, etc., which are in the problem of the epoxy resin (Patent Documents 9 to 11). However, the silicone resin has a lower glass transition temperature as compared with that of the epoxy resin that has been used in the conventional mounting substrate, so that the resin itself involves the problem of dimensional stability, and there is a problem of warpage due to thinning the substrate. In addition, when a copper foil clad laminated substrate is prepared, an adhesive force to the metal foil is insufficient and reliability is poor, and the problem of unfastening or twisting of the glass fiber which occurs at the time of pressing under heating and pressure has not yet been solved by the reason that it uses a surface-treated glass fiber similarly to the above-mentioned glass epoxy substrate, whereby it has been desired to develop a laminated substrate excellent in heat resistance and weather resistance, and further having good dimensional stability.
Thus, it has been reported a metal clad laminated substrate in which a glass silicone resin laminated substrate which had previously been laminated and molded at a high temperature is heat treated, an organometallic compound is impregnated thereinto and thermally decomposed, and then, a thermoplastic fiber film and a metal foil are superimposed and molded (Patent Document 12). In this method, whereas an adhesive force to the copper foil is improved, in fact, a polyimide film is used as the thermoplastic fiber film, so that an insulating layer surface of the substrate is colored to yellow which is derived from the polyimide resin from the initial stage. Therefore, it is difficult to expand the substrate into a substrate for mounting an LED or solar cell modules. In addition, a glass silicone laminated substrate is used so that there is a problem in flexibility, and there are still problems in unfastening or twisting of the glass fiber.